title: Electroencephalogram slowing in rapid eye movement sleep behavior disorder is associated with mild cognitive impairment.
abstract: BACKGROUND
  Idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD) is a well-documented risk factor for synucleinopathies such as Parkinson disease (PD) and dementia with Lewy bodies (DLB). Moreover, approximately 50% of iRBD patients have mild cognitive impairment (MCI). The purpose of our study was to investigate waking electroencephalogram (EEG) abnormalities specific to iRBD patients with MCI.
  
  
  METHODS
  Forty-two polysomnographically confirmed iRBD patients, including 23 iRBD [+]MCI patients 19 patients without MCI (iRBD [-]MCI), and 37 healthy subjects participated in the study. All participants underwent a complete neuropsychologic assessment for MCI diagnosis and a waking quantitative EEG recording.
  
  
  RESULTS
  iRBD [+]MCI patients had a higher slow-to-fast frequency ratio than iRBD [-]MCI patients and controls in the parietal, temporal, and occipital regions. iRBD [+]MCI patients also had higher relative θ power in the parietal, temporal, and occipital regions and lower relative α power in the occipital region compared to iRBD [-]MCI patients and controls. Moreover, iRBD [+]MCI patients had higher relative θ power in the frontal and central areas and lower relative β power in the central, parietal, and temporal regions compared to controls. The dominant occipital frequency also was slower in iRBD [+]MCI patients compared to controls. No between-group differences were observed between iRBD [-]MCI patients and controls.
  
  
  CONCLUSIONS
  In iRBD patients, only those with concomitant MCI showed waking EEG slowing in the posterior cortical regions, providing a potential marker for an increased risk for developing DLB or PD.
authors.affiliation: Center for Advanced Research in Sleep Medicine, Hôpital du Sacré-Cœur de Montréal, Montreal, Quebec, Canada; Department of Psychology, Université de Montréal, Montreal, Quebec, Canada.
authors.forename: Jessica
authors.initials: J
authors.lastname: Rodrigues Brazète
authors.forename: Jacques
authors.initials: J
authors.lastname: Montplaisir
authors.forename: Dominique
authors.initials: D
authors.lastname: Petit
authors.forename: Ronald B
authors.initials: RB
authors.lastname: Postuma
authors.forename: Josie-Anne
authors.initials: JA
authors.lastname: Bertrand
authors.forename: Daphné
authors.initials: D
authors.lastname: Génier Marchand
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Gagnon
mesh_terms: D000368:Aged; D002540:Cerebral Cortex / Q000503:physiopathology; D060825:Cognitive Dysfunction / Q000150:complications / Q000503:physiopathology*; D004569:Electroencephalography; D005260:Female; D006801:Humans; D020961:Lewy Body Disease / Q000150:complications / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000150:complications / Q000503:physiopathology; D017286:Polysomnography; D020187:REM Sleep Behavior Disorder / Q000150:complications / Q000503:physiopathology*; D014851:Wakefulness / Q000502:physiology*
keywords: Dementia with Lewy bodies; Electroencephalography; Mild cognitive impairment; Parkinson’s disease; REM sleep behavior disorder; Spectral analysis